Most of liquid crystal display devices that perform color display include color filters that allow red (R), green (G), and blue (B) lights to be transmitted therethrough for respective three subpixels into which one pixel is divided. However, since about two-thirds of backlight light that is irradiated onto a liquid crystal display panel is absorbed by the color filters, a liquid crystal display device of a color filter system has a problem of low light use efficiency. Hence, attention is focused on a liquid crystal display device of a field sequential system that performs color display without using color filters.
In the field sequential system, one frame period which is a display period of one screen is divided into three subframe periods. During a first subframe period, a red screen is displayed by allowing red light sources to emit light while a red component of a video signal is inputted. During a second subframe period, a green screen is displayed by allowing green light sources to emit light while a green component of the video signal is inputted. During a third subframe period, a blue screen is displayed by allowing blue light sources to emit light while a blue component of the video signal is inputted. Since the liquid crystal display device of the field sequential system displays red, green, and blue screens in turn in such a manner, a viewer can visually recognize color video by an afterimage effect. As such, since the liquid crystal display device of the field sequential system does not require color filters, the light use efficiency improves by about three times compared to the liquid crystal display device of the color filter system.
Patent Document 1 describes that by receiving a video signal added with content identification information during a blanking period, optimum processing according to the type of content is performed on the video signal based on the content identification information. In addition, Patent Document 2 describes that a system that handles two-system video signals: a first video signal for displaying OSD (On Screen Display) video and a second video signal for displaying different video than the OSD video, transmits OSD information added to a blanking period of the second video signal.